This invention relates to a light source device having a lamp, and relates to a projection-type image display device using the light source device.
A light source device used in a projection-type image display device includes a lamp unit and a lamp cartridge in which the lamp unit is housed. The lamp unit includes a lamp (such as a metal halide lamp or a xenon lamp) and a reflection mirror. Conventionally, there is a case where an arc tube of the lamp is broken (due to the increase of internal pressure) while the lamp is turned on, and therefore it is necessary to prevent components in the projection-type image display device from being damaged by fragments (i.e., broken pieces) of the lamp. For this purpose, there is provided a lamp unit having an encapsulated structure in which a transparent plate (such as a glass plate) closes an opening of the light emitting side of the reflection mirror, as disclosed in, for example, Japanese Laid-Open Publication No. HEI 8-7841 (Page 2, FIG. 1).
However, in such a lamp unit having the encapsulated structure, the temperature of the interior of the reflection mirror (i.e., a space surrounded by the reflection mirror and the transparent plate) tends to increase due to an arc between electrodes while the lamp is turned on. Further, in these days, the luminance of the projection-type image display device increases, and therefore the output of the lamp also increases, with the result that the temperature of the interior of the reflection mirror tends to increase. As a result, there are problems that the lifetime of the lamp may be shortened, the luminance may be reduced, and the breakage of the lamp may easily occur.
In order to solve these problems, there is proposed a light source device having a ventilation opening formed on the reflection mirror for circulating the air. In such a light source device, it is necessary to prevent the fragments of the lamp from being scattered out of the light source device (i.e., in the projection-type image display device) via the ventilation opening. Therefore, a mesh member (made of metal) is provided to cover the ventilation opening, as disclosed in, for example, Japanese Patent Publication No. 3275755 (Pages 1-2, FIG. 1) and Japanese Laid-Open Patent Publication No. HEI 10-254061 (Pages 4-5, FIG. 1). Additionally, there is proposed another light source device configured to open the ventilation opening when the light source device is mounted in the projection-type image display device, and to close the ventilation opening when the light source device is detached from the projection-type image display device, as disclosed in Japanese Laid-Open Patent Publication No. 2002-107823 (Page 2, FIG. 8).
However, if the mesh member closes the ventilation opening (as disclosed in Japanese Patent Publication Nos. 3275755 and Japanese Laid-Open Patent Publication No. HEI 10-254061), the mesh member needs to be formed in accordance with the shape of the ventilation opening. Further, if a plurality of ventilation openings are formed on the reflection mirror, it is necessary to provide a plurality of mesh members for covering the respective ventilation openings.
Moreover, the reflection mirror and the transparent plate are generally made of hard-cutting material (i.e., quarts glass), and therefore the shape of the ventilation opening is limited, and the tolerance is relatively large, in terms of manufacturing method and manufacturing cost. In order to prevent the small fragments of the lamp from being scattered via a clearance between the ventilation opening and the mesh member, it is necessary to take measures to fill in the clearance, and therefore the manufacturing cost may increase. Further, if the mesh member is not properly fixed to the ventilation opening of the reflection mirror, the lamp unit itself becomes a defective unit, and therefore yield ratio is lowered.
Furthermore, a ventilation opening is also formed on the lamp cartridge in accordance with the position and the shape of the ventilation opening of the reflection mirror. Therefore, a common lamp cartridge can not be used for different lamp units whose reflection mirrors have different ventilation openings in shape or position.
Additionally, in the light source device configured to open and close the ventilation opening of the reflection mirror (as disclosed in Japanese Laid-Open Patent Publication No. 2002-107823), the ventilation opening is not closed when the breakage of the lamp occurs, and therefore it is not possible to prevent the fragments of the lamp from being scattered out of the light source device (i.e., in the projection type image display device). Further, there is a possibility that the fragments of the lamp may be carried by the cooling air to the exterior of the image display device.